The mechanism by which single neurons in the striate cortex of the cat acquire their motion-direction selectivity is being analyzed. We record from Brodmann's Area 17, trying to maintain our microelectrode within the subregion of the striate area to which the area centralis projects, and its immediate surround. Our preparation is paralyzed and anesthetized with nitrous oxide. After using hand-mapping to locate the receptive field and its optimal orientation, a systematic analysis is carried out. We use four different types of stimuli in our analysis. (1) Continuously moving rectangles, oriented optimally, and moving in the preferred direction and then in the null direction (where such a motion-direction selectivity is shown). We vary both velocity and edge contrast in different experiments. (2) Static, optimally oriented rectangles are flashed for 400 msec durations, at various locations within the receptive field. (3) We present a sequence of two static rectangles, one coming on somewhat later than the other (the so-called stimulus onset asynchrony or SOA). This display is similar to apparent movement displays used with human subjects for the analysis of apparent movement perception. The main experimental parameter here is SOA. (4) We present rectangles within the various portions of the receptive field and modulate the intensity of the rectangle sinusoidally. By using these various displays, we analyze the properties of the motion-direction selective networks.